python 2 is no longer supported

* m4/pypath.m4: Check for Python 3.2+.
* README, NEWS, HACKING: Reflect this change.

HACKING

@@ -32,6 +32,7 @@ since the generated files they produce are distributed.)
   Perl, with its Gettext module (it might be called something like
     liblocale-gettext-perl or p5-locale-gettext in your distribution)
   A complete LaTeX distribution, including latexmk.
+  Python >= 3.2, IPython >= 2.3
 
 Bootstrap the GIT tree by running
 

NEWS

@@ -132,6 +132,9 @@ New in spot 1.99b (not yet released)
 
     - Boost is not used anymore.
 
+    - The Python bindings now assume Python 3.2 or later.
+      (In other words, Python 2 is not supported anymore.)
+
     - The tgba_succ_iterator interface has changed.  Methods next(),
       and first() should now return a bool indicating whether the
       current iteration is valid.

README

@@ -6,8 +6,7 @@ and LIP6. It provides algorithms and data structures to implement
 the automata-theoretic approach to LTL model checking.
 
 It is mainly meant to be used as a C++ library, but it also comes with
-a few handy command-line utilities, and some (limited) Python
+a few handy command-line utilities, and some Python bindings.
-bindings.
 
 Keeping in touch
 ================
@@ -31,7 +30,7 @@ Requirements
 Spot requires a C++11-compliant compiler.
 G++ 4.8 or later, as well as Clang++ 3.5 or later should work.
 
-Spot expects a complete installation of Python (version 2.0 or later).
+Spot expects a complete installation of Python (version 3.2 or later).
 Especially, Python's headers files should be installed.  If you don't
 have Python installed, and do NOT want to install it, you should run
 configure with the --disable-python option (see below).
@@ -39,9 +38,8 @@ configure with the --disable-python option (see below).
 Optional third-party dependencies
 ----------------------------------
 
-If the SAT-solver glucose is found on your system, it will
+If the SAT-solver glucose is found on your system, it will be used by
-be used by our test suite to test our SAT-based minimization
+our test suite to test our SAT-based minimization algorithm.
-algorithm.
 
 Spot used to distribute a modified version of LBTT (an LTL to Büchi
 test bench), mostly fixing errors reported by recent compilers.
@@ -64,11 +62,12 @@ In addition to its usual options, ./configure will accept some
 flags specific to Spot:
 
   --disable-python
-    Turn off the compilation of Python bindings.  These bindings are
+    Turn off the compilation of Python bindings.  These bindings offers a
-    currently used to run a couple of tests, and to build the CGI
+    convenient interface with used in an IPython notebook, and are
-    script that translates LTL formulae on-line.  You may safely
+    also used to build the CGI script that translates LTL formulae
-    disable these, especially if you do not have a working Python
+    on-line.  You may safely disable these, especially if you do not
-    installation or if you are attempting some cross-compilation.
+    have a working Python 3.2+ installation or if you are attempting
+    some cross-compilation.
 
   --enable-devel
     Enable debugging symbols, turn off aggressive optimizations, and

m4/pypath.m4

@@ -1,5 +1,5 @@
 AC_DEFUN([adl_CHECK_PYTHON],
- [AM_PATH_PYTHON([2.0])
+ [AM_PATH_PYTHON([3.2])
   case $PYTHON in
     [[\\/$]]* | ?:[[\\/]]* );;
     *) AC_MSG_ERROR([The PYTHON variable must be set to an absolute filename.]);;